Devices of this nature must very frequently be cleaned, because during preparation of foods with circulating vapor or a circulating vapor-hot air mixture, precipitates are deposited on the wall by the heat carriers, which deposits have escaped the food items. This is especially the case when preparing good-sized roasts, since the juice, even if only to a slight extent, is distributed on the walls. These precipitates would, if they were not removed, lead to deposits, which would become encrusted on the walls due to the effect of heat. In order to clean the cooking chamber, it is sprayed with a cleaning solution, following which subsequently for a given time vapor is introduced into the cooking chamber, so that the deposits are loosened. Subsequently, the cooking chamber must be washed. Since this process is time consuming and cumbersome, because facilities of this nature frequently have a large cooking chamber, which, especially in the back regions, can be reached by hand only with difficulty. Moreover, temperatures in the cooking chamber following the vapor process are relatively high.